1. Field of the Invention
The present invention relates to a solar cell and its method of manufacture, and more particularly, the present invention relates to a solar cell having improved efficiency and its method of manufacture.
2. Description of the Related Art
A solar cell generates electric energy using solar energy. The solar cell is eco-friendly and has an infinite energy source and a long life span. The solar cell includes a silicon solar cell and a dye-sensitized solar cell.
The silicon solar cell includes a semiconductor substrate and an emitter layer that have different conductivity types to form a PN junction, a first electrode electrically connected to the emitter layer, and a second electrode electrically connected to the semiconductor substrate.
In general, the emitter layer is formed by a high-temperature diffusion method, a printing method or a spray method. Since the high-temperature diffusion method uses a diffusion furnace, the high-temperature diffusion method has poor productivity and is not suitable for a large-sized device. Since the printing method uses an expensive material, the printing method has a large material loss and poor productivity. In the spray method, a compound containing a dopant is sprayed onto a surface of the semiconductor substrate and the dopant is diffused by a high-temperature heating treatment, thereby forming the emitter layer. The spray method has better productivity than the other methods.
However, while the compound containing the dopant that is used in the spray method is hydrophilic, the semiconductor substrate is hydrophobic. Accordingly, the compound containing the dopant cannot be formed on the semiconductor substrate with certainty. In addition, since the compound containing the dopant is vaporized in the high-temperature heating treatment, a sufficient amount of dopant cannot be diffused into the semiconductor substrate. Therefore, since it is difficult to form the emitter layer having an appropriate concentration, PN junction characteristics deteriorate.